Electrical condenser and method of making the same



Feb. 14, 1928. 1,658,817

W. H. PRIESS ELECTRICAL CONDENSER AND METHOD OF MAKING THE SAME FiledDec. 5, 1 2 Sheets-Sheet 1 Feb. 14, 1928.

W. H. PRIESS ELECTRICAL CONDENSER AND METHOD OF MAKING THE SAME 5, 19212 Sheets-Sheet 2 Filed Dec.

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Smvewtoz Prim Patented Feb. 14, 1928.

UNITED STATES 1,658,817 PATENT OFFICE.

WILLIAM H. PRIESS, OF BELMONT, MASSACHUSETTS, ASSIGNOR TO WIRELESS SPE-CIALTY APPARATUS COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF NEWYORK.

ELECTRICAL CONDENSER AND METHOD OF MAKING THE SAME.

Application filed. December 5, 1921. Serial No. 519,867.

This invention relates to electrical condensers and methods of makingthe same. In particular, the invention is applicable to small micacondensers for use as magneto condensers or in ignition systems or forother purposes.

An object of the invention is a condenser of simple but effectiveconstruction which can be manufactured at low cost, all as moreparticularly pointed out hereinafter.

The invention consists of the condenser structure including thearrangement of parts hereinafter disclosed.

In the accompanying drawings, T have illustrated one embodiment of myinvention in which Figure 1 is a plan view, on an enlarged scale, of theassembled condenser;

Fig. 2 is an elevation of the same;

Fig. 3 is a sectional elevation thereof on the line 3-3 of Fig. 1, on anenlarged scale, the stack being illustrated in elevation;

Fig. 4 is a detail perspective view of one of the clamping plates;

Fig. 5 is a detail perspective view of an insulating sheath for thecondenser;

Fig. 6 is a detail perspective view of one of the condenser foilarmatures;

Fig. 7 is a detail perspective view of a clip plate;

Fig; 8 is a detail perspective view of a eh i;

Fig. 9 is an elevation of a mica sheet used in building the stack; and

Fig. 10 is an elevation of the other clamping plate, the first beingshown in Fig. 4.

In the construction of the condenser of the present invention, the stackS is built up of alternate sheets of foil 1 (Fig. 6) and square sheetsof dielectric such as mica 1 (Fig. 0) having rounded corners. As clearlyshown in Fig. 6, the foil sheets 1, of simple contour, are provided withtabs 3, 4, which are so arranged during the bu1lding of the stack as toproject alternately at spaced points as at opposite sides of thestaclcas illustrated in Figs. 1 and 2 at 3, 4. Preferably the micasheets, before the stackis built, are varnished. This varnishing may bedone by the method described in my pending application 377 .977, filedApr l 30, 1920. After the required number of foil sheets and dielectricshave been assembled into a stack, the stack is baked and then tested forvoltage and capacity as described 1n my eo-pending application abovementioned. It is to be understood, however, that any suitable method ofassembling and treating the stack may be employed.

After the condenser stack of the simple square contour above describedhas been finished, the projecting foil tabs constituting terminals 3 and4 are out 01f or clipped by any suitable means such as anelectrically-heated strip. The foil ends or terminals 3 and 4respectively are then dipped into a low melting point alloy having amelting point lower than the melting point of the toil employed in thecondenser, whereby the foils of like polarity in the respective groups oand 4 of opposite polarity are positively connected together in goodelectrical contact. This alloy preferably consists of two parts tin andone part bismuth, which is main tained at a temperature of approximately180 to 190 (1., the melting point of the foil employed being around 230C. The alloy has a melting point of approximately 150 to 160 C. Hence,there-is no tendency to melt 0E the tin toll of the projecting tabs 3, tin soldering, and a good soldered joint is secured, providing acondenser in which there are no floating foils, and in which theelectrical connection between foils of like polarity is not dependentupon the pressure on the stack.

The stack S is now assembled in its clamp C, which comprises a stifimetal clamp plate 5 (Fig. 10)' engaging one end face of stack S. Thisplate 5 is preferably of brass and is providecbat its opposite ends withapertured ears 5.

The type of condenser disclosed herein by way of example is desi ned asto shape, etc, to fit into standar ignition systems casings (notillustrated) and is desi 'ed to be electrically connected to the brea erbox and easing as Well as the coil of such ignition systems, all ofwhich, being of well-known design, need not be illustrated. For thispurpose, the clamping plate 5 is provided with a projecting stud 6adapted to fit into an insulated bore of the ignition casing or boxing,this stud, when the condenser is assembled in the ign tion casingpbeingelectrically connected to the breaker box by means of a screw adapted tobe threaded into the threaded bore in stud 6 as illustrated in Fig. 2.Interposed between the stack S and the plate 5, however, is a sheet 7 ofinsulation, (Figs. 2 and 3), preferably of fish paper.

Upon the opposite end face of the stack is placed a square sheet of mica8 (Fig. 3) of the general size and shape of the dielectric sheets ofmica 1 (Fig. 9) constituting the condenser stack, although preferablyslightly thicker, and upon this sheet 8 rests a metal terminal or clipplate 9 illustrated in Fig. 7 and'adapted to be stamped out from sheetmetal. Clip plate 9 is providedat one side with an apertured tongue orlug 10 whereby the condenser and its assembled clamp may be securedwithin and to the casing of. the ignition device by any desired securing means. At an opposite portion of the plate 9 is a depending tab 11,adapted to be electrically connected to the terminal 3 of the condenserstack as illustrated in Figs. 1 and 2. Connected to plate 9 in spacedrelation to the tab 11 is an integral clip 12 projecting beyond thestack S and having tabs 13 thereon adapted to be bent over a wire lead(not illustrated) connected to the ignition coil, which lead may besoldered to the clip 12, ifso desired. Stamped sheet metal terminalplate 9 constitutes a stiff member the main body of which lies in thestack and an integral portion of which, as 10, extends outside the stackas a stiff portion adapted for attach- "ment thereto of a circuit leadwithout injuring the terminal plate itself or its integral projection;and such stiff projecting portion is advantageous in resisting bendingwhich might result in short circuiting or in damaging the insulation,and in permitting mechanical mounting of the. condenser. top of the clipplate 9 is located a second sheet 14 (Fig. 3) of insulating material,such as mica, and located upon the sheet 14 is the opposite metalclamping plate 15 separately shown in Fig. 4 as comprising at oppositesides thereof apertured ears 15 adapted for co-operation with theapertured ears 5? of bottom clamp plate 50f Fig. 10. Plate 15 is aspringplate which, when not under compression, is curved as illustrated inFig. 4.

Metal rivets or other securing means 16 extend through the aperturedears 15*" and 5 (of clamp plates 15 and 5 respectively), and are spunover to secure the plates 5 and 15 together in clamping relation againstthe stacks. Plate 15, as well as the entire clamp C, Fig. 3, includingplate 5 and rivets 16, is

thoroughly insulated from the clip plate 9 and, upon the securement ofthe rivets, the plate 15 is flattened out as illustrated in Fig. 2,whereby uniform spring pressure is exerted over the active area of thestack while the condenser is in service. Plate 15 may come prise anysuitable springy materialsuch as phosphor bronze.

The rivets or other securing means 16 are spaced a substantial distancefrom the sides of stack and from the sheets of foil and dielectricconstituting the stack and from terminal plate 9, and are entirelyindependent thereof. The rivets connecting plates 5 and 15 are spun overto secure the plates together as indicated at 17 (Fig. 2). A single pairof oppositely-arranged rivets is sufiicient to hold the stack 'underuniform compression by means of the clamp C, Fig. 3 and to flatten outspring plate 15. The foil terminal 3, constituting the common terminalof the foils of one polarity, is connected-by a lead 18 (Fig. 2) to thedepending tongue 11 of clip or terminal plate 9 of Fig. 7, while theother terminal 4 of the condenser (Fig. 2) is electrically connected tothe clamp C as through one of the rivets 16 by a copper lead 19,soldered to the rivet as illustrated in Figs. 1 and 2. The clamp C,including the clamping plates 5 and 15 and rivets 16, constitutes thehigh potential terminal of the condenser, while the plate 9, insulatedfrom the clamp by sheets 8 and 14, constitutes the low potentialterminal.

As above mentioned, the low potential en of the stacks is connectedbvt-he clip 12 (Fig. 7 to the ignition coil, while the high potentialend of the stack is likewise connected to this coil when the condenseris assembled in the ignition system device, by means of a metal clip 20,Fig. 8, mounted upon plate 15 and secured thereto by one of the rivets16, the clip 20 having an opening through which the rivet passes. Thisclip 20 is provided with tabs 21, to which the lead from the ignitioncoil may be secured or soldered. The clip is held against dislocation ormovement around the rivet as an axis by means of a pair of prongs 22thereon, which when the condenser is assembled are bent around the edgesof an adjacent ear 15 of the plate 15 (Fig. 4) as illustrated in Figs. 1and 2.

\Vhen the condenser has been assembled as above described, an insulatingsheath 23 (Fig. 5), preferably of fish paper, is placed around thecondenser and its clamp as illustrated in Figs. 1-3. This member 23 isprovided with a central hole 24 through which the stud 6 (Figs. 2-3) isadapted to extend. Sheet 23 also is provided with lateral stack-casingportions 25.

After the member 23 has been placed around'the condenser, the condenseris placed within the ignition system box or casing, and

the tab 10 of clip or terminal plate 9 of Fig. 7 is secured to the same,as a circuit terminal extending between clamp plates 5 and 15 be-Lesser;

The stud 6, which is insulated from such casing, is then electricallyconnected to the breaker box, whereby the high potential end of thecondenser is electrically connected to the breaker box. The leads fromthe ignition coil are then connected or soldered to the clips 12 and 20.

The condenser of this invention is much cheaper than the ignitioncondensers now in use, for the reason that assembling costs have beenreduced on account of the simple symmetrical contour of the sheets offoil and dielectric. Furthermore, the amount of mica necessary for aiven capacity is less, matcrially reducing the area and thickness of thestack, making a more compact and smaller condenser as well as reducingthe cost. The number of rivets is reduced to a minimum, two or morelocated at opposite sides of the stack in spaced relation thereto beingample to secure plates 3 and 15 together with sulficient pressure uponthe stack to maintain the sheets in intimate contact, the spring plate15 providing means to allow expansion of the stack under heatingconditions. In the condenser of the present invention, there are nofloating plates, the foil sheets of like polarity having good electricalcontact with each other and with the clip plate 9 or with the condenserclamp C itself. The metal parts of the condenser may be easily stampedout from sheet metal, and then manufacture and assembly may be done veryeasily and at low cost. Inasmuch as the rivets are independent of themica, the highest degree of pressure may be obtained without danger ofsplitting the mica, this pressure maintaining the sheets of foil anddielectric in intimate contact It is to he understood that the inventionis not limited to the embodiments and features specifically shown anddescribed here in, but that such embodiments and features are subject tochanges and modifications without any departure from the spirit of theinvention,

1' claim 1. An electrical condenser which comprises a stack of sheets ofmetal foil and mice and a metal clip-plate at one end of the stack andhaving insulating sheets on both its faces; the foils having partsextending beyond the micas and clip-plate; metal clamping plates onopposite ends of the stack, one of which lies against the insulatinsheet outside the clip-plate, and both of w ich are connected togetherin clamping relation with the stack at points external to the stack oilsheets and clip-plate; means electrically connecting togather the foilextensions of like polarity; said clip-plate loeing formed with adepending tongue; and a lead connection between one set of foilconnections and said tongue.

2. In an electrical condenser, the combination with a stack of condensersheets of metal foils and dielectrics, of at least three metal platesstacked together with said condenser sheets and extending oversubstantially the entire active areas of the condenser sheets in thestack; two of said metal plates lying as clamping members on the endfaces of the stack and holding the condenser sheets tightly togetherthroughout their active areas; and said third plate constituting acondenser terminal by being connected to the stack foils of one polarityand insulated from the end clamping plates but lying between them andthereby subjected to their compres-' sion and held from lateraldisplacement; and securing means extending from a clamping plate at oneend of the stack to the clamping plate at the other end, said securingmeans holding the two clamping plates in their compressing relation withthe stack sheets and said condenser terminal plate.

An electrical condenser which comprises a stack of sheets of metal foilsand mica, the foils having parts projecting beyond the micas at oppositeparts of the stack and constituting foil-terminals of opposite polarity;metal soldering together the foil-sheets of the foil terminals outsidethe stack and having a lower melting point than the foil-sheets; twometal clamping plates on the respective stack-ends and projecting beyondthe 'mica sheets from the same sides of the stack as the foil-terminalsbut extending beyond the latter; rivets located outside the stack andconnecting together the clamping-plate extensions; and a metal leadelectrically connecting one set of foil-terminal-extensions so solderedwith the adjacent rivet of the clamping plates.

4:. In an electrical condenser, a stack havmg terminals, a clamp forsaid stack comprising a pair of plates arranged upon opposite ends ofthe stack, means for mechanically connecting said plates, a clip plateassociated with said stack and said clamp and insulated therefrom, saidclamping plates and clip-plate extending over substantially the entireactive areas of the condenser sheets, and means electrically connectingone terminal of the stack to said clip plate and electrically connectingsaid clamp to the other terminal of said stack.

5. In an electrical condenser, a stack comprising alternate sheets offoil and dielectrio and having terminals, a clip plate mounted at oneend of the stack and insulated therefrom, clamping plates enclosing saidstack and clip plate and insulated therefrom, rivets arranged uponopposite sides of the stack and spaced therefrom and connecting saidclamping plates, means electrically connecting one terminal of thecondenser to said clip plate, means electrically connecting the oppositeterminal of said condenser to the clamp, and a clip secured to saidclamp.

6. In an electrical condenser, a stack comill lilt

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prising alternate sheets of foil and dielectrio, a clip plate comprisinga depending tongue, a clip member and securing member mounted with saidstack and insulated therefrom, clamping plates enclosing said stack andclip plate, insulated therefrom and provided with )rojecting earsextending beyond the stac rivets extending through said projecting earsand connecting said damping plates, means electrically connecting thefoil of one polarity to said depending tongue, means electricallyconnecting the opposite foil of said condenser stack to said clamp, anda clip on one of said rivets and provided with prongs engaging oppositeedges of an ear of one of said clamping plates, whereby it is securedagainst movement.

7. In an electrical condenser, a stack of symmetrical sheets ofdielectrlc and sheets 4 of foil having tabs projecting alternately,

clamping plates upon opposite sides of the stack and connected togetherin clamping relation to the stack at points external of the stack, aplate interposed between said stack and clamp and insulated from saidclamp, said clamping plates and interposed plate extending oversubstantially the entire active areas of the condenser sheets and meanselectrically connecting said alternate tabs to said clamp andintermediate plate respectively.

8. In an'electrical condenser, a stack of alternate sheets of foil anddielectric, clamping plates on opposite end faces of said stack, rivetsconnecting said plates, and a separable clip mounted on one of saidrivets wand having prongs engaging a clamping plate to prevent themovement thereof on the rivet.

9. In an electrical condenser the combination with a stack of condensersheets of metal foils and dielectrics. of at least three metal platesstacked together with said eon--' by subjected to the compressionthereof and held from lateral displacement; and securing means extendingfrom a clamping plate at one end of the stack to the clamping plate atthe other end and holding the clamp ing plates in their compressingrelation with the condenser sheets and condenser terminal plate.

10. An electrical condenser comprising a stack of dielectric sheets andmetal foil armatures; a stiff sheet metal terminal plate located againstand covering the end face of the stack and c'onductively connected tothe stack foils of one polarity thereby constituting said plate aterminal of the stack; a pair of sheet metal clamping plates locatedagainst and covering the end faces of the stack; and extending oversubstantially the entire active areas of the condenser sheets;

sheet insulation between said terminal plate and the adjacent clampingplate; sheet insulation between the other end of the stack and the otherclamping plate; and securing means holding the clamping plates inclamping relation to the stack and terminal plate; said terminal platehaving an integral stiif circuit terminal portion extending from andbeyond a side of the stack and between said clamping plates.

11. An electrical condenser comprising a stack of dielectric sheets andmetal foil armatures: a stitf sheet metal plate located against an endface of the stack and constituting a terminal thereof; metal clampingmeans acting on the ends of the stack and clamping the stack and saidterminal plate between them; and extending over substantially theentireactive areas of the condenser sheets; and said terminalplate beinginsulated from said clamping means and having an integral stiff circuitterminal portion extending from and beyond a side of the stack andbetween the clamping-means on the stack ends. I

12.- An electrical condenser comprising a stack of dielectric sheets andmetal foil armatures; a stifi' sheet metal plate located against an endface of the stack and constituting avterminal of the stack; a pair of..sheet metal clamping plates located against the opposite end faces ofthe stack; and extending over substantially the entire active areas ofthe condenser sheets; said terminal plate being insulated from saidclamping plates; and riveting means holding the clamping plates inclamping relation to the stack and said terminal plate; said terminalplate having an integral stiff circuit termina-l portion extending fromand beyond a side of the stack and between said clamping plates.

13. An electrical condenser comprising a stack of dielectric sheets andmetal foil armatures; a stiff sheet metal plate located against an endface of the stack and conductively connected to the stack foils of onepolarity therebyconstituting said plate a terminal of the stack"; metalclamping means acting on the ends of the stack and clamping the stackand said terminal plate, said clamping means being Insulated from saidterminal plate and conductively connected to the stack foils of oppositepolarity there llo by constituting said clamping means as anotherterminal of the stack; and extending over substantially the entireactive areas of the condenser sheets; said terminal plate having anintegral stifl circuit terminal portion extending from and beyond a sideof the stack and between the clamping means on the stack ends.

14. An electrical condenser comprising a stack of dielectric sheets andmetal foil armatures; a stiff sheet metal terminal plate located againstan end face of the stack and constituting a terminal of the stack; metalclamping means acting on the ends of the stack and clamping the stackand said terminal plate, said clamping means being insulated from saidterminal plate and constituting another terminal of the stack; andextending over substantially the entire active areas of the condensersheets; said terminal plate having an integral still circuit terminalportion extending from and beyond a side of the stack and between theclamping means on the stack ends.

WILLIAM H. PRIESS

